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https://www.readbyqxmd.com/read/29775312/limits-of-directed-self-assembly-in-block-copolymers
#1
Karim Raafat Gadelrab, Yi Ding, Ricardo Pablo-Pedro, Hsieh Chen, Kevin W Gotrik, David G Tempel, Caroline A Ross, Alfredo Alexander-Katz
Understanding the conditions under which defects appear in self-assembling soft-matter systems is of great importance, for example, in the development of block-copolymer (BCP) nanolithography. Here, we explore the limits of directed self-assembly of BCPs by deliberately adding random imperfections in the template. Our results show that defects emerge due to local "shear-like" distortions of the polymer-template system, a new mechanism that is fundamentally different from canonical mechanisms of 2D melting...
May 18, 2018: Nano Letters
https://www.readbyqxmd.com/read/29742897/in-situ-synthesis-of-ternary-block-copolymer-homopolymer-blends-for-organic-photovoltaics
#2
Fritz Nübling, Dan Yang, Peter Muller-Buschbaum, Martin Brinkmann, Michael Sommer
A detailed investigation of in-situ synthesized all-conjugated block copolymer (BCP) compatibilized ternary blends containing poly(3-hexylthiophene) (P3HT) and poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dibcarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (PNDIT2) as donor and acceptor polymers, respectively, is presented. Both polymers are incompatible and show strong segregation in blends, which renders compatibilization with their corresponding BCPs promising to enable nanometer-phase separated structures suitable for excitonic devices...
May 10, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29739210/intradomain-phase-transitions-in-flexible-block-copolymers-with-self-aligning-segments
#3
Christopher J Burke, Gregory M Grason
We study a model of flexible block copolymers (BCPs) in which there is an enlthalpic preference for orientational order, or local alignment, among like-block segments. We describe a generalization of the self-consistent field theory of flexible BCPs to include inter-segment orientational interactions via a Landau-de Gennes free energy associated with a polar or nematic order parameter for segments of one component of a diblock copolymer. We study the equilibrium states of this model numerically, using a pseudo-spectral approach to solve for chain conformation statistics in the presence of a self-consistent torque generated by inter-segment alignment forces...
May 7, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29737829/one-step-anionic-copolymerization-enables-formation-of-linear-ultra-high-molecular-weight-block-copolymer-films-featuring-vivid-structural-colors-in-the-bulk-state
#4
Michael Appold, Eduard Grune, Holger Frey, Markus Gallei
Ultra-high molecular weight (UHMW) tapered block copolymers (BCPs) consisting of polyisoprene-block-poly(4-methylstyrene) (PI-b-P4MS) featuring overall molar masses in the range of 1101 to 2033 kg mol-1 (Mw) are synthesized via a convenient one-step anionic copolymerization protocol. The obtained UHMW BCPs are investigated by differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and 1H NMR spectroscopy. Microphase separation for the UHMW block copolymers in the bulk state is investigated by transmission electron microscopy (TEM) measurements and scanning electron microscopy (SEM) revealing well-ordered lamellar and spherical domains with large domain sizes in the range of 100 to 200 nm...
May 8, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29733499/unravelling-correlation-between-charge-mobility-and-cocrystallization-in-rod-rod-block-copolymer-for-high-performance-field-effect-transistors
#5
Mingjing Zhu, Shuang Pan, Yue Wang, Ping Tang, Feng Qiu, Zhiqun Lin, Juan Peng
The ability to capitalize on the cocrystallization strategy involving two or more components aggregating into cocrystals renders the creation of materials and devices with markedly improved charge mobility. This, however, has yet to be largely explored in all-conjugated block copolymers (BCPs). Herein, we report on the first investigation into the correlation between cocrystals and charge mobility in a series of new all-conjugated BCPs, namely, poly(3-butylthiophene)-b-poly(3-hexylselenophene) (P3BT-b-P3HS) with varied P3BT/P3HS block ratios for high-performance field-effect transistors...
May 7, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29706666/characterizing-the-interface-scaling-of-high-%C3%AF-block-copolymers-near-the-order-disorder-transition
#6
Daniel F Sunday, Michael J Maher, Adam F Hannon, Christopher D Liman, Summer Tein, Gregory Blachut, Yusuke Asano, Christopher J Ellison, C Grant Willson, R Joseph Kline
Advancements in the directed self-assembly of block copolymers (BCPs) have prompted the development of new materials with larger effective interaction parameters ( χ e ). This enables BCP systems with phase separation at increasingly small degrees of polymerization ( N ). Very often these systems reside near the order-disorder transition and fit between the weak and strong segregation limits where the behavior of BCP systems is not as thoroughly understood. Utilizing resonant soft X-ray reflectivity (RSoXR) enables both the BCP pitch ( L 0 ) and interface width ( w M ) to be determined simultaneously, through a direct characterization of the composition profile of BCP lamellae oriented parallel to a substrate...
January 9, 2018: Macromolecules
https://www.readbyqxmd.com/read/29691006/radical-scavenging-activity-of-sulfated-bupleurum-chinense-polysaccharides-and-their-effects-against-oxidative-stress-induced-senescence
#7
Haibin Tong, Xiaoli Zheng, Jianxi Song, Jian Liu, Ting Ren, Xu Zhang, Luqi Huang, Mingjiang Wu
In this study, BCPS-1, a polysaccharide previously isolated and characterized from Bupleurum chinense was chemically modified to yield two sulfated derivatives, which we designated as S-BCP1-4 and S-BCP1-8 . The physicochemical properties of these sulfated derivatives were then determined by high performance liquid chromatography (HPLC), Fourier transform infrared spectrometry (FT-IR), and gas chromatography (GC), and then compared with those of BCPS-1. Furthermore, the antioxidant activities of all three polysaccharides were also evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay, superoxide radical assay and hydroxyl radical assay, while their effects against H2 O2 -induced cellular senescence were determined using senescence-associated β-galactosidase (SA-β-gal) staining, cell cycle assay and immunoblotting in H2 O2 -induced mouse lung endothelial cells (MLECs)...
July 15, 2018: Carbohydrate Polymers
https://www.readbyqxmd.com/read/29683466/anatomy-of-triply-periodic-network-assemblies-characterizing-skeletal-and-inter-domain-surface-geometry-of-block-copolymer-gyroids
#8
Ishan Prasad, Hiroshi Jinnai, Rong-Ming Ho, Edwin L Thomas, Gregory M Grason
Triply-periodic networks (TPNs), like the well-known gyroid and diamond network phases, abound in soft matter assemblies, from block copolymers (BCPs), lyotropic liquid crystals and surfactants to functional architectures in biology. While TPNs are, in reality, volume-filling patterns of spatially-varying molecular composition, physical and structural models most often reduce their structure to lower-dimensional geometric objects: the 2D interfaces between chemical domains; and the 1D skeletons that thread through inter-connected, tubular domains...
April 23, 2018: Soft Matter
https://www.readbyqxmd.com/read/29681131/an-electron-density-source-function-study-of-dna-base-pairs-in-their-neutral-and-ionized-ground-states-%C3%A2
#9
Carlo Gatti, Giovanni Macetti, Russell J Boyd, Chérif F Matta
The source function (SF) decomposes the electron density at any point into contributions from all other points in the molecule, complex, or crystal. The SF "illuminates" those regions in a molecule that most contribute to the electron density at a point of reference. When this point of reference is the bond critical point (BCP), a commonly used surrogate of chemical bonding, then the SF analysis at an atomic resolution within the framework of Bader's Quantum Theory of Atoms in Molecules returns the contribution of each atom in the system to the electron density at that BCP...
April 21, 2018: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/29667409/ionic-liquids-as-additives-to-polystyrene-b-poly-methyl-methacrylate-enabling-directed-self-assembly-of-patterns-with-sub-10-nm-features
#10
Xuanxuan Chen, Chun Zhou, Shuang-Jun Chen, Gordon S W Craig, Paulina Rincon-Delgadillo, Takahiro Dazai, Ken Miyagi, Takaya Maehashi, Akiyoshi Yamazaki, Roel Gronheid, Mark Stoykovich, Paul F Nealey
Polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is one of the prototypical block copolymers (BCPs) in directed self-assembly (DSA) research and development, with standardized protocols in place for processing on industrially relevant 300 mm wafers. Scaling of DSA patterns to pitches below 20 nm using PS-b-PMMA, however, is hindered by the relatively low Flory-Huggins interaction parameter,χ. Here we investigate the approach of adding small amounts of ionic liquids (IL) into PS-b-PMMA, which selectively segregates into the PMMA domain and effectively increases the χ parameter and thus the pattern resolution...
April 18, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29656527/self-assembly-of-rod-coil-block-copolymers-on-carbon-nanotubes-a-route-toward-diverse-surface-nanostructures
#11
Yang Han, Chunhua Cai, Jiaping Lin, Shuting Gong, Wenheng Xu, Rui Hu
In this work, it is reported that poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers (BCPs) can disperse carbon nanotubes (CNTs) in solution and form various surface nanostructures on the CNTs via solution self-assembly. In an organic solvent that dissolves the BCPs, the PBLG rod blocks adsorb on CNT surfaces, and the BCPs form conformal coatings. Then, by the introduction of water, a selective solvent for PEG blocks, the BCPs in the coatings further self-assemble into diverse surface nanostructures, such as helices (left-handed or right-handed), gyros, spheres, and rings...
April 14, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/29649121/synthesis-of-hydroxyapatite-%C3%AE-tricalcium-phosphate-and-biphasic-calcium-phosphate-particles-to-act-as-local-delivery-carriers-of-curcumin-loading-release-and-in-vitro-studies
#12
Despoina Xidaki, Panagiota Agrafioti, Dimitra Diomatari, Archontia Kaminari, Eleftherios Tsalavoutas-Psarras, Polyxeni Alexiou, Vasilios Psycharis, Effie C Tsilibary, Spyridon Silvestros, Marina Sagnou
The successful synthesis of hydroxyapatite (HA), β-Tricalcium phosphate (β-TCP) and two biphasic mixtures (BCPs) of the two was performed by means of wet precipitation. The resulting crystals were characterized and the BCP composition was analyzed and identified as 13% HA-87% TCP and 41% HA-59% TCP. All samples were treated with curcumin solutions, and the degree of curcumin loading and release was found to be proportional to the TCP content of the ceramic. No further cytotoxicity was observed upon MG-63 treatment with the curcumin-loaded ceramics...
April 12, 2018: Materials
https://www.readbyqxmd.com/read/29611253/responsive-block-copolymer-photonic-microspheres
#13
Yi Yang, Hodae Kim, Jiangping Xu, Min-Soo Hwang, Di Tian, Ke Wang, Lianbin Zhang, Yonggui Liao, Hong-Gyu Park, Gi-Ra Yi, Xiaolin Xie, Jintao Zhu
Responsive photonic crystals (PCs) have attracted much attention due to their broad applications in the field of chemical and physical sensing through varying optical properties when exposed to external stimuli. In particular, assembly of block copolymers (BCPs) has proven to be a robust platform for constructing PCs in the form of films or bulk. Here, the generation of BCPs photonic microspheres is presented with 3D periodical concentric lamellar structures through confined self-assembly. The structural color of the spherical PCs can be tuned by selective swelling of one block, yielding large change of optical property through varying both layer thickness and refraction index of the domains...
April 2, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29528628/computational-investigation-of-carbene-phosphinidenes-correlation-between-31-p-chemical-shifts-and-bonding-features-to-estimate-the-%C3%AF-backdonation-of-carbenes
#14
Sayan Dutta, Bholanath Maity, D Thirumalai, Debasis Koley
Detailed investigations of the electronic structure and bonding scenario in different carbene-phosphinidenes have been presented using state-of-the-art computational methods (BP86/def2-TZVPP//BP86/def2-SVP). We have endeavored to find the correlation of the calculated 31 P chemical shifts with different bonding parameters of compounds to access the relative π-acceptor strengths of the carbenes. 31 P chemical shifts exhibit a weak correlation with σ-polarizations of Ccarb -P bonds toward phosphorus; however excellent correlations are obtained in the case of π-polarizations of Ccarb -P bonds toward the carbene carbon (Ccarb ) and NPA charges on phosphorus atoms...
April 2, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29516614/rapid-one-step-synthesis-of-complex-architecture-block-polymers-using-inductively-armed-disarmed-monomer-pairs
#15
Boyce S Chang, Stephanie Oyola-Reynoso, Joel Cutinho, Martin M Thuo
A facile method is reported for rapid, room-temperature synthesis of block copolymers (BCP) of complex morphology and hence nontraditional spherical assembly. The use of solvated electrons generates radical anions on olefinic monomers, and with a felicitous choice of monomer pairs, this species will propagate bimechanistically (via radical and the anion) to form BCPs. Molecular weight of the obtained BCP range from Mw = 97 000-404 000 g mol-1 (polydispersity index, PDI = 1.4-3.0) depending on monomer pairs...
April 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/29462964/behavior-of-the-e-e-bonds-e-e-s-and-se-in-glutathione-disulfide-and-derivatives-elucidated-by-quantum-chemical-calculations-with-the-quantum-theory-of-atoms-in-molecules-approach
#16
Satoko Hayashi, Yutaka Tsubomoto, Waro Nakanishi
The nature of the E-E' bonds (E, E' = S and Se) in glutathione disulfide ( 1 ) and derivatives 2 - 3 , respectively, was elucidated by applying quantum theory of atoms-in-molecules (QTAIM) dual functional analysis (QTAIM-DFA), to clarify the basic contribution of E-E' in the biological redox process, such as the glutathione peroxidase process. Five most stable conformers a - e were obtained, after applying the Monte-Carlo method then structural optimizations. In QTAIM-DFA, total electron energy densities H b ( r c ) are plotted versus H b ( r c ) - V b ( r c )/2 at bond critical points (BCPs), where V b ( r c ) are potential energy densities at BCPs...
February 17, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29400453/competitive-self-assembly-kinetics-as-a-route-to-control-the-morphology-of-core-crystalline-cylindrical-micelles
#17
Jiangping Xu, Hang Zhou, Qing Yu, Ian Manners, Mitchell A Winnik
Nucleated self-assembly in selective solvents of core-crystalline block copolymers (BCPs) is a special case of living supramolecular polymerization, leading to rodlike micelles of controlled and uniform length. For the crystallization-driven self-assembly of PFS-containing BCPs (PFS = polyferrocenyldimethylsilane), the formation of block comicelles by sequential addition of different BCPs is well-established. But there are only a few examples of living copolymerization, the simultaneous addition of pairs of BCPs with different corona-forming chains...
February 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29390179/directed-self-assembly-of-asymmetric-block-copolymers-in-thin-films-driven-by-uniaxially-aligned-topographic-patterns
#18
Dong-Eun Lee, Jaegeon Ryu, Dongki Hong, Soojin Park, Dong Hyun Lee, Thomas P Russell
We present a simple, versatile approach to generate highly ordered nanostructures of block copolymers (BCPs) using rubbed surfaces. A block of poly(tetrafluoroethylene) (PTFE) was dragged across a flat substrate surface above the melting point of PTFE transferring a highly aligned PTFE topographic pattern to the substrate. Si wafer, glass, and polyimide films were used as substrates. Thin films of cylinder-forming asymmetric polystyrene-block-poly(2-vinylpyridine) copolymers (S2VPs) were solvent annealed on the surfaces having the transferred surface pattern to induce their directed self-assembly...
February 27, 2018: ACS Nano
https://www.readbyqxmd.com/read/29383370/simultaneous-uniaxial-extensional-deformation-and-cylindrical-confinement-of-block-copolymers-using-non-equilibrium-molecular-dynamics
#19
George L Shebert, Yong Lak Joo
Using coarse-grained nonequilibrium molecular dynamics, symmetric block copolymers are simulated under the combined effects of cylindrical confinement and uniaxial extensional deformation. For a given confinement diameter, a block copolymer (BCP) will self-assemble into a fixed number of concentric cylinder lamellae at equilibrium. The changing diameter during uniaxial extensional deformation therefore is expected to affect the morphology of the BCPs. The aim of this study is to investigate the interplay of deformation and confinement on BCP morphology by varying the simulation strain rate and diameter...
February 21, 2018: Soft Matter
https://www.readbyqxmd.com/read/29329645/polysaccharides-extracted-from-the-roots-of-bupleurum-chinense-dc-modulates-macrophage-functions
#20
Zhi-De Zhang, Hong Li, Fen Wan, Xiao-Yu Su, Yan Lu, Dao-Feng Chen, Yun-Yi Zhang
The present study aimed to investigate the effects of polysaccharides extracted from Bupleurum chinense DC (BCPs) on macrophage functions. In the in vivo experiment, 1 mL of 5% sodium thioglycollate was injected into the abdomen of the mice on Day 0 and macrophages were harvested on Day 4. The macrophages were cultured in plates and treated with different concentrations of BCPs and stimulus. Effects of BCPs on macrophage functions were assessed by chemotaxis assay, phagocytosis assay and Enzyme-Linked Immunosorbent Assay (ELISA)...
December 2017: Chinese Journal of Natural Medicines
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